Bidoof and Bibarel

Bidoof
The Plump Mouse Pokémon
Type: Normal
Official Registration #: 399
Entry: A two-foot-tall rodent-like pokémon common to the Sinnoh region. Although it looks cute, unassuming, and dim-witted, bidoof are actually among the most destructive and dangerous beginner-level rodent pokémon in existence, even more so than its cousin the rattata. The reason why is that while rattata are quick to flee from danger and while many rattata forage alone, bidoof are tenacious, brave, and prone to forming large foraging groups. Therefore, whereas a rattata can be scared away by the presence of a trained machamp, a bidoof will merely tilt its head, emit a rallying cry, and charge forward with hundreds of its fluffy, biting brethren in tow. Needless to say, trainers would be wise to take caution around the mighty bidoof.

Bibarel
The Beaver Pokémon
Type: Normal/Water
Official Registration #: 400
Entry: The evolved form of bidoof, by battle experience. While many other pokémon develop a longing for wandering or expanding their territories upon evolution, bibarel becomes more domesticated. That is to say, rather than attempting to expand its territory, bibarel spends most of its efforts focusing on very specific points of rivers, where it builds giant dams where it will raise its young. These dams have been known to have huge ecological impacts. For most humans, they become a blessing, as in building the dam, the bibarel may create a natural reservoir or divert a river to a village in dire need of water. However, it should be noted that bibarel are largely oblivious to any damage their actions may cause, and they still retain their tendency to congregate in large groups from their time as bidoof. As such, in very certain cases, large numbers of bibarel have been known to singlehandedly flood entire Sinnohean towns without even realizing it.